Concentric knurl ball joint

ABSTRACT

A replacement ball joint assembly ( 10 ) adapted to be pressed into a previously used and possibly distorted receiving hole ( 26 ) in a suspension component such as a control arm ( 28 ). A socket housing ( 12 ) of the assembly ( 10 ) includes a plurality of generally annular, concentric knurls ( 36 ) each having a respective crest portion ( 38 ) and separated one from another by intervening relief grooves ( 40 ). The crest portions ( 38 ) of the knurls ( 36 ) may be tapered so as to provide a lead-in feature to minimize misalignment during a press-in installation operation. The knurls ( 36 ) are preferably softer than the control arm material so that they yield during press-in rather than further disfiguring or enlarging the receiving hole ( 26 ). Displaced material from the crest portions ( 38 ) of the knurls ( 36 ) flows into the relief grooves ( 40 ).

CROSS REFERENCE TO RELATED APPLICATIONS

None.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a press-fit type ball joint the type used inautomobile and light truck applications, and more particularly toward areplacement ball joint assembly adapted to be pressed into a previouslyused and possibly distorted receiving hole in a suspension component.

2. Related Art

Suspension systems in many automobiles and light trucks include severalball joint assemblies to provide a pivoting, swiveling connection withthe wheels. Ball joints typically comprise spherical bearings connectingupper and/or lower control arms to the respective steering knuckles,like that shown in FIG. 1. Such assemblies have a limited life span andrequire replacement when indications of wear present. It is not uncommonto replace a ball joint assembly numerous times over the service life ofa typical automobile or light truck.

Ball joint assemblies usually have a socket housing that is mounted in areceiving hole in one of the control arms. These socket housings can bemounted using various techniques such as by direct threaded engagement,taper fit with a threaded nut keeper, spot welding, or by press-fit.Press-fit ball joint assemblies are held in place by a tightinterference fit between an exterior socket housing and the innerreceiving hole in the control arm. Knurls on the socket housing improveretention. Frequently, a snap ring is used to backup the press-fitconnection to assure the socket housing does not inadvertentlydisconnect.

Replacement ball joint assemblies, i.e., ball joint assemblies providedas repair parts rather than original equipment components, are oftendesigned with oversized knurls in the form of longitudinally extendingsplines so as to assure a tight interface with the receiving hole in thecontrol arm. An example of this type is shown, for example, in FIG. 3. AC-frame press tool, like that shown in FIG. 2, may be used to remove theold, worn ball joint assembly and install a new, replacement ball jointassembly according to well known procedures. These procedures mayinclude use of a sleeve-type receiving tube and cup-like adapter likethose illustrated in FIG. 2.

A particular problem experienced by mechanics and others involved in theautomobile repair trade involves the replacement of a press-fit typeball joint into a control arm having a worn and/or disfigured receivinghole. For example, if a particular vehicle has experienced multipleprevious ball joint assembly replacement operations, it is likely thatthe receiving hole in the control arm will have become distorted andenlarged, and possibly also work-hardened by the numerous previous balljoint replacement operations. In these cases, it may be recommended toreplace the entire control arm that is only deficient due to a worn andover-expanded receiving hole. As will be appreciated, this can result inincreased repair costs, unnecessary waste, and consumer dissatisfaction.Accordingly, there is a need in the art to address situations where areplacement ball joint assembly of the press-fit type is required to beinstalled in a previously used and possibly distorted receiving hole ina vehicular suspension component. Furthermore, there is a need toprevent further distortion of a receiving hole to thereby extend theuseful life of control arms and other such suspension components.

SUMMARY OF THE INVENTION

This invention relates to an assembly and method for replacing a balljoint assembly of the press-fit type into a previously used and possiblydistorted receiving hole in a vehicular suspension component. The balljoint assembly comprises a socket housing defining a central axis. Thesocket housing includes an exterior side wall having a lead-in end andan axially spaced exterior stop flange. A moveable member having a ballhead portion is pivotally captured in the socket housing and furtherincludes a mounting shaft extending generally axially from the ball headportion. The exterior side wall of the housing includes a plurality ofgenerally annular knurls each having a respective crest portionestablishing its outer diameter. The knurls are axially separated onefrom another by intervening relief grooves. Each knurl is disposedconcentrically about the central axis. At least the first knurl adjacentthe lead-in end has a smaller outer diameter than the last knurladjacent the stop flange. A replacement ball joint assembly constructedaccording to these specifications is particularly well suited toachieving a secure press-fit connection in a previously used andpossibly distorted receiving hole in a vehicular suspension component.

According to another aspect of this invention, a method is provided forreplacing a ball joint assembly in a vehicular suspension componentcomprising the steps of: providing a vehicular suspension componenthaving a worn-out ball joint lodged in a receiving hole and thenremoving the worn-out ball joint from the suspension component to exposethe receiving hole therein. The method further includes providing areplacement ball joint assembly having an exterior side wall with alead-in end and an axially spaced exterior stop flange. A plurality ofgenerally annular knurls are formed about the exterior side wall, eachknurl having a crest portion establishing an outer diameter thereof. Theknurl forming step further includes reducing the outer diameter of thefirst knurl adjacent the lead-in end relative to the outer diameter ofthe last knurl adjacent the stop flange. Each knurl is separated fromthe next adjacent knurl by an intervening relief groove. The methodincludes forcibly pressing the replacement ball joint into the exposedreceiving hole in the suspension component while simultaneouslydisplacing crest material from at least one of the knurls into animmediately adjacent relief groove in response to attrition with thereceiving hole.

The subject invention overcomes the shortcomings and disadvantagesinherent in prior art press-fit ball joint assemblies. The concentricorientation of the knurls, together with the intervening relief grooves,work in concert to diminish further distortion of the receiving hole inthe suspension component while simultaneously preventing the undesirablebuildup of displaced material under the stop flange, thereby minimizingstress and receiving hole distortion during installation.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily appreciated when considered in connection with thefollowing detailed description and appended drawings, wherein:

FIG. 1 is an exemplary, fragmentary view of a vehicular wheel and itsassociated suspension components including an upper control arm, lowercontrol arm and steering knuckle, with press-fit style ball jointassemblies disposed there between;

FIG. 2 is an exemplary view of a press-fit ball joint assembly beinginstalled into a lower control arm using a C-frame press tool,installation sleeve and adapter;

FIG. 3 is an enlarged view of a prior art socket housing enlarged fromthe area circumscribed at 3 in FIG. 2 and showing the traditional axial,spline-like knurls;

FIG. 4 is a cross-sectional view of a replacement ball joint assemblyaccording to the subject invention;

FIG. 5 is a fragmentary elevation showing a replacement ball jointassembly according to the subject invention poised for insertion into areceiving hole in a suspension component;

FIG. 6 is a fragmentary view like that in FIG. 5 but further advanced todepict the first knurl adjacent the lead-in end of the socket housingserving as a pilot feature to reduce the tendency for misalignment;

FIG. 7 is a view as in FIG. 6 showing a still further advancement withthe ball joint assembly in a fully seated condition;

FIG. 8 is an enlarged, fragmentary view of a portion of the exteriorside wall of the socket housing illustrating a tapered, lead-in angleformed by the crests of the respective knurls in one embodiment of theinvention; and

FIG. 9 is another enlarged view showing the forcible pressing of areplacement ball joint assembly into an exposed receiving hole in asuspension component whereby crest material from the relatively softknurls is displaced into the relief grooves in response to attritionwith the receiving hole, whereby damage to the inside diameter of thereceiving hole is minimized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, wherein like numerals indicate like orcorresponding parts throughout the several views, a replacement balljoint assembly according to the subject invention is generally shown at10 in FIG. 4. The assembly 10 includes a cup-like socket housing 12,preferably formed from a metal such as steel, in which is captured thearticulating ball head portion 14 of a ball stud 16, also preferablyformed from steel or other suitable material. The ball stud 16 includesa mounting shaft 18 that extends integrally away from the ball headportion 14, outwardly from the socket housing 12. The mounting shaft 18may have a tapered connection surface and a threaded end 20, althoughthe specific shapes and attachment techniques for the mounting shaft 18may vary from one application to the next.

The socket housing 12 defines a central axis A, and includes an exteriorside wall having a lead-in end 22 and an axially spaced exterior stopflange 24. In practice, the lead-in end 22 is inserted first into areceiving hole 26 in a suspension component 28, as viewed in FIGS. 5 and6. During a press-fit operation, the socket housing 12 is forced, suchas through application of the screw of a C-frame tool, until the stopflange 24 abuts the suspension component 28 in surface-to-surfacecontact as shown in FIG. 7. The socket housing 12 may include a ringgroove 30 for receiving a snap ring or other type of supplementalretention device once the assembly 10 has been seated in the suspensioncomponent 28.

A dust boot 32 may be employed, as needed, to provide an enclosure toseal the socket housing 12 from external contaminants as well as toretain the lubricant or grease at the articulating interface with theball head portion. The assembly 10 is adapted to receive grease or otherlubricant through a grease fitting 34.

Turning now to FIGS. 5-9, the socket housing 12 is shown in enlargeddetail to better illustrate the exterior side wall of the socket housing12. The portion of the exterior side wall between its lead-in end 22 andstop flange 24 is configured with a plurality of generally annularknurls 36. Each knurl 36 has a crest portion 38 which establishes itsrespective outer diameter. The knurls 36 are axially separated from oneanother by intervening relief grooves 40. As perhaps best shown in FIGS.8 and 9, flanks 42 of each knurl 36 extend almost radially tointerconnect each side of its crest 38 to an adjacent relief groove 40.A back-up relief groove 44 is disposed between the last knurl 36B andthe stop flange 24.

The knurls 36 are preferably formed in a machining operation so as tominimize the effects of work-hardening, thereby maintaining the materialhardness of the knurls 36 in the softest possible condition.Furthermore, the knurls 36 are formed so that the first knurl 36Aadjacent the lead-in end 22 has a smaller outer diameter than the lastknurl 36B adjacent the stop flange 24. The smaller first knurl 36A isdesigned, relative to the receiving hole 26 in the suspension component28 to provide a piloting or lead-in feature to help center the balljoint assembly 10 during installation and thereby prevent inadvertentmisalignment or damage to the suspension component 28. Preferably, thisrelative sizing results in a repair scenario in which pressing of theball joint assembly 10 into the suspension component 28 experiences aninterference fit between at least the last knurl 36B and the receivinghole 26 but not between the crest of the first knurl 36A and thereceiving hole 26. In one preferred embodiment, the crests 38 of all theknurls 36 are aligned with a frusto-conical taper like that illustratedin FIG. 8, wherein the broken line represents a cylinder equivalent indiameter to the last knowl 36B. The broken line in FIG. 9 represents thetheoretical cylindrical edge of a receiving hole 26, and highlights themanner in which the degree of interference between the crests 38 and thereceiving hole 26 increases in the direction of the last knurl 36B. Inan alternative configuration, all of the crests 38 may have a truecylindrical exterior configuration but merely stepped diametersproviding similar functionality. In yet another variation, only thefirst two or three knurls 36A, 36 are formed with a tapered lead-inconfiguration on their crests 38, whereas the remaining knurls 36leading up to the last knurl 36B are each formed with a propercylindrical configuration. Of course, many other variations are possiblewithout departing from the spirit of this invention.

Referring again to FIGS. 8 and 9, it can be observed that each knurl 26has an axial width while each relief groove 40 has an axial span. Thedimensional relationships between the knurls 36 and grooves 40 is such,in one exemplary embodiment, that the axial width of each knurl 36 isgreater than the axial span of each relief groove directly adjacentthereto by approximately 50%. A configuration like that depicted hereprovides an advantageous blend of installation convenience, holdingpower and alignment functionality without the shortcomings found inprior art designs like that of FIG. 3. More specifically, the reliefgrooves 40, 44 backing each respective knurl 36 allow for displacedcrest material (evident from the curls illustrated in FIGS. 7 and 9) toflow during the installation process. Traditional axial knurl designslike that of FIG. 3 do not allow for this flow of material and, as aresult, cause a buildup of displaced material which can accumulate underthe stop flange of the housing, thereby creating a buildup of pressureduring installation. This shortcoming is avoided by the subjectinvention where such displaced crest material flows directly into anadjacent relief groove 40, 44 without the undesirable buildup of stressand pressure. As a result, the inside diameter of the receiving hole 26is better preserved, thereby enabling the possibility of future repairor replacement operations.

As shown in FIG. 5, the knurls 36 are preferably substantially annularand discrete. However, those of skill in the art will appreciate that inan alternative configuration the knurls 36 could be cut in a thread-likepattern resulting in something of an Acme-style thread pattern whilestill maintaining other relationships and attributes as described above.Such an alternative configuration would result in generally annularknurls instead of the substantially annular knurls depicted in thedrawings.

As alluded to previously, the knurls 36 and associated relief grooves 40are preferably machined into the metallic socket housing 12 usingconventional machine techniques. In other words, material may be removedfrom the socket housing 12 with a cutting tool. This compares totraditional processes which require high pressure forging to unseat thematerial and form the spline-like knurls as shown in FIG. 3. Machining,on the other hand, provides for much better process control and lesswear on the machine tools. The design furthermore improves theinstallation of the ball joint assembly 10 by a mechanic. Suchinstallation improvements are attributed to the formation of the lead-intaper on the first knurl 36 and possibly on additional knurls 36 as wellso that the socket housing 12 can be received at least initially intothe receiving hole 26 in the correct orientation. In addition, thelatter concentric knurls 36, 36B are designed to wipe away duringinstallation, thereby preserving the inside diameter of the matingreceiving hole 26 instead of damaging the receiving hole like intraditional axial knurl designs.

The generous relief grooves 40 provide space for displaced crestmaterial to flow into during the press-in process. This avoids theproblems associated with traditional knurl designs (FIG. 3) whichincubate a build-up of displaced material under the stop flange of thehousing, thereby causing undesirable stress concentrating as well asfurther damage/distortion to the receiving hole 26.

The foregoing invention has been described in accordance with therelevant legal standards, thus the description is exemplary rather thanlimiting in nature. Variations and modifications to the disclosedembodiment may become apparent to those skilled in the art and fallwithin the scope of the invention. Accordingly the scope of legalprotection afforded this invention is defined by the following claims.

What is claimed is:
 1. A vehicular suspension assembly comprising: avehicle suspension component having a receiving hole which is generallycylindrical in shape; a socket housing defining a central axis, saidsocket housing including an annular exterior side wall having a lead-inend and an axially spaced exterior stop flange; a moveable member havinga ball head portion pivotally captured in said socket housing and amounting shaft extending generally axially therefrom; said exterior sidewall of said housing further including a plurality of generally annularknurls each having a respective crest portion establishing an outerdiameter, said plurality of knurls being axially separated one fromanother by intervening relief grooves, each of said knurls disposedconcentrically about said central axis; and a plurality of said knurlsadjacent said lead-in end having a smaller outer diameter than a lastsaid knurl adjacent said stop flange, wherein said plurality of knurlsadjacent said lead-in end taper towards said lead-in end; the outerdiameter of at least one of said plurality of knurls adjacent saidlead-in end being smaller than said diameter of said receiving hole insaid suspension component while the outer diameter of said last knurl islarger than said diameter of said receiving hole whereby pressing ofsaid ball joint assembly into said suspension component creates aninterference fit between at least said crest of said last knurl and saidreceiving hole but not between said crest of at least one of saidplurality of knurls adjacent said lead-in end and said receiving hole.2. The assembly of claim 1 wherein each of said plurality of knurlsadjacent said lead-in end has a frustoconically tapered crest portion.3. The assembly of claim 1 wherein said last knurl adjacent said stopflange has a true cylindrical crest portion.
 4. The assembly of claim 1wherein each said knurl has an axial width and each said relief groovehas an axial span; the axial width of each said knurl being greater thanthe axial span of each said relief groove directly adjacent thereto. 5.The assembly of claim 1 wherein each said knurl is substantiallyannular.
 6. The assembly of claim 1 wherein said knurls each includemachined flanks interconnecting said respective crest portions with adirectly adjacent said relief groove.
 7. The assembly of claim 1 furtherincluding a back-up relief groove disposed between said last knurl andsaid stop flange.
 8. The assembly of claim 1 wherein said receiving holeof said vehicle suspension component is used.
 9. The assembly of claim 8wherein said used receiving hole is distorted.
 10. A replacement balljoint assembly adapted to be pressed into a receiving hole in a vehiclesuspension component, said assembly comprising: a vehicle suspensioncomponent including a receiving hole having a generally cylindricalshape with a generally constant internal diameter; a socket housingdefining a central axis, said socket housing including an annularexterior side wall having a lead-in end and an axially spaced exteriorstop flange; a moveable member having a ball head portion pivotallycaptured in said socket housing and a mounting shaft extending generallyaxially therefrom; said exterior side wall of said housing furtherincluding a plurality of generally annular knurls each having arespective crest portion establishing an outer diameter, said pluralityof knurls being axially separated one from another by intervening reliefgrooves, each of said knurls disposed concentrically about said centralaxis; a plurality of said knurls adjacent said lead-in end having asmaller outer diameter than a last said knurl adjacent said stop flange,wherein each of said plurality of knurls adjacent said lead-in end has afrustoconically tapered crest portion and said plurality of knurlsadjacent said lead-in end taper towards said lead-in end; the outerdiameter of said plurality of knurls adjacent said lead-in end beingsmaller than said diameter of said receiving hole in said suspensioncomponent while the outer diameter of said last knurl is larger thansaid diameter of said receiving hole whereby pressing of said ball jointassembly into said suspension component creates an interference fitbetween at least said crest of said last knurl and said receiving holebut not between said crest of said plurality of knurls adjacent saidlead-in end and said receiving hole.
 11. The assembly of claim 10wherein said last knurl adjacent said stop flange has a true cylindricalcrest portion.
 12. The assembly of claim 10 wherein each said knurl hasan axial width and each said relief groove has an axial span; the axialwidth of each said knurl being greater than the axial span of each saidrelief groove directly adjacent thereto.
 13. The assembly of claim 10wherein each said knurl is substantially annular.
 14. The assembly ofclaim 10 wherein said knurls each include machined flanksinterconnecting said respective crest portions with a directly adjacentsaid relief groove.
 15. The assembly of claim 10 wherein said suspensionmember is fabricated from a material having a definable materialhardness, and said socket housing is fabricated from a material having adifferent material hardness which is softer than the material hardnessof said suspension member.
 16. The assembly of claim 10 wherein saidreceiving hole of said vehicle suspension component is used.
 17. Theassembly of claim 16 wherein said used receiving hole is distorted.